Rechargeable electrochemical storage systems are presently becoming increasingly important in many areas of everyday life. In addition to the long-standing applications as automobile starter batteries and as an energy source for portable electronic devices, considerable growth is predicted in the future for electric automobile drives and for stationary energy storage. Traditional lead/sulfuric acid accumulators are not suitable for the new applications because their capacity is far too low, and they cannot be cycled frequently enough. In contrast, the best prospects are seen with lithium batteries.
However, lithium accumulators according to the prior art likewise have too little energy storage capacity for many applications. Present lithium-ion batteries have specific energy densities between approximately 100 and 250 Wh/kg. In addition, they usually contain costly elements such as cobalt and/or nickel. Lithium/sulfur and lithium/air systems have much higher (theoretical) energy densities:
Theoretical energy densityBattery systemWh/LWh/kgLi ion (LiC6/Ni, Mn, Co oxide)1710510Lithium/sulfur27102450Lithium/air5830
The technical challenges in the development of Li/air systems are still so great that a marketable system is not expected for at least another 10-20 years (M. Jacoby, Chem. Eng. News Nov. 22 (2010) 29-31). The prospects for the lithium/sulfur system appear to be much more favorable. One drawback of this system is the use of lithium metal anodes. Lithium metal is relatively costly compared to saline materials or the graphite used in lithium-ion batteries. In addition, this battery has the further disadvantage that it loses capacity too rapidly during charging and discharging.